Monte Carlo Simulation For Transient Radiative Transfer In Multi-dimensional Inhomogeneous Media

The appearance of ultrashort pulse lasers in the picosecond and femtosecond levelled to the development of many industrial fields. It’s a very important link in theapplication of engineering and medical fields to deeply understand the transmissionmechanism of ultrashort laser pulses in the medium and the thermal physicalphenomena. Transient radiative transfer is different from the steady-state radiativetransfer, there must be a unique physical phenomenon in the medium, especially in aninhomogeneous medium.Inhomogeneous media widely present in nature and engineering applications. Thetypical inhomogeneous medias includ turbid media, multi-layer media, gradientrefractive index media etc., such as biological tissue, the spacecraft multi-layerprotective structure, atmosphere and sea water. Many areas are involved in the mediumto solve the transient radiative transfer problems still exist many difficulties up to now.The problem of transient radiative transfer in an absorbing, emitting, and scatteringmedium are numerically studied in this article. Modify Monte Carlo method is used toestablish a non-uniform two-dimensional rectangular media radiative transfer model.Duhamel’s superposition theorem is introduced into the solution scheme, andtime-domain radiative transfer factor concept is combined with to solve time-domainradiation information.The main research contents in this paper are displayed as follows:(1)The establishment of a transient radiative transfer model of two-dimensionalinhomogeneous rectangular media by Monte Carlo method is equivalent to aone-dimensional uniform panel, one-dimensional multi-layers media, one-dimensionalgraded refractive index distribution medium and two-dimensional uniform mediumrespectively. And the results are compared with the other existing data. Some physicalphenomenon of transient radiative transfer are explained in this article.(2)A transient radiative transfer model of two-dimensional multi-layer media isestablishment to calculate the transient radiative information of the rectangulardielectric, and interface reflection characteristics are considered in the calculation tofind the influence in the results of time-domain radiation information, the albedo, refractive index distribution, optical thickness and the other optical properties areconsidered as well.(3)On the basis of the radiative transfer model of two-dimensional multi-layermedia, we establish a transient radiative transfer model in a two-dimensional gradedrefractive index medium, according to the principal of multi-layers approximation. Theinfluenses of one-way refractive index layer change and radial sinusoidal change areconsidered in this article, the refractive index distribution, albedo, anisotropic scatteringand the other optical properties are considered as well.